The present invention relates to a cutting blade and method used for a pavement cutting apparatus that cuts pavement of an asphalt road or a concrete road in a circle for installation of a manhole or the like.
In the case of manhole installation on pavement, a pavement cutting apparatus for cutting pavement in a circle (hereafter called a cutting apparatus) has so far been used to perform circular cutting of pavement at a manhole installation point. As this type of cutting apparatus, an applicant of the present invention has already proposed the apparatus shown in FIG. 15.
The apparatus shown in FIG. 15 can rotate around an axis 50a of a main driving shaft and can simultaneously move up and down along the axis 50a. An end of a radially projecting arm 51 is fixed to the lower end of the main driving shaft 50. A cutting blade 52 is fixed to another end of said arm 51. Associated with rotation of the main driving shaft 50 arranged vertically with respect to pavement R in such a way that the axis 50a of the main driving shaft 50 points a center P of a pavement circular-cut section Ra, a cutting blade 52 travels along the circumference of a cut circle C and simultaneously goes downward as the main driving shaft 50 lowers, thereby cutting the pavement in a circle.
When an edge of the cutting blade 52 cuts gradually the pavement R and penetrates the back of the pavement, the pavement circular-cut section Ra is cut off from the pavement R as shown in FIG. 16. A manhole is installed in the circular hole left in the pavement R after the section Ra is taken out of the pavement R.
However, conventional cutting apparatuses have a problem that the pavement circular-cut section R is hardly taken out of the pavement R. This is because the pavement circular-cut section Ra cut from the pavement R moves to a ground G due to its own weight as shown by dashed dotted line in FIG. 16 and falls below a pavement surface, and is thereby difficult to be taken out. In particular, when the ground G under the pavement R is softer, the pavement circular-cut section Ra falls more deeply so that it is extremely difficult to be taken out.
It is an object of the present invention to overcome the aforementioned problem by providing a cutting blade and method used for a pavement cutting apparatus that cuts pavement in a circle so that a circular-cut section cut off from the pavement can be easily taken out of the pavement.
A cutting blade for cutting pavement in a circle, connected to an end of a radially-projecting arm attached to a driving shaft arranged vertically with respect to a center of the circle, and moved downwardly and simultaneously rotated along a circumference of the circle of the pavement to be cut,
wherein a cutting blade body having a pavement cutting edge at a bottom thereof is inclined to the center of the circle to be cut, the pavement cutting edge serves as a tip for cutting the pavement and side edges of the cutting blade body serve as an inclined cutting surface to bore an inside of the pavement cut by the pavement cutting edge, thereby cutting the pavement in a frusto-conical shape.
The cutting blade body is flat in shape and attached to a holder in a slanting direction with respect to the pavement, and the holder is connected with the arm.
More specifically, in the pavement cutting apparatus comprising the main driving shaft rotatable about its axis to be vertically arranged with respect to the pavement, an end of the radially projecting arm to be attached to the lower end of the main driving shaft, and the cutting blade attached to the other end of said arm to be moved along the circumference of a pavement circle to be cut in conjunction of rotation of said main driving shaft, and simultaneously moved toward the pavement by a movement drive means and, thereby cutting the pavement, the inclined cutting face is provided on said cutting blade.
In the aforementioned cutting apparatus, the cutting blade travels along the circumference and simultaneously the cutting face with its cutting edge set inward in a slanting direction goes straight ahead in the slanting direction so that the pavement cutting proceeds. Thus, a diameter of the cut circle reduces gradually from top to bottom and it is minimized at the bottom. As a result, the circularly cut section of the pavement can moves upwards but not downward because, when moving downward, it collides against a non-cut section of the pavement. That is, a cut surface of the non-cut section of the pavement supports the circularly cut section of the pavement from below so as to completely prevent the circularly cut section from falling into the ground. Thus, the circularly cut section of the pavement can be easily taken out of the pavement.
In the cutting blade, a radially-projecting stepped portion is provided with the cutting blade body above the pavement cutting edge, thereby cutting the pavement in a stepped shape above the frusto-conical shape.
Alternatively, the present invention provides a cutting blade for cutting pavement in a circle, connected to an end of a radially-projecting arm attached to a driving shaft arranged vertically with respect to a center of the circle, and moved downwardly and simultaneously rotated along a circumference of the circle of the pavement to be cut,
wherein a cutting blade body having a pavement cutting edge at a bottom thereof is positioned in a direction perpendicular to the pavement and a triangled-shaped inclined cutting edge is fixed to an upper portion of the cutting blade body above the pavement cutting edge, the pavement cutting edge serves as a tip for cutting the pavement and the triangled-shaped inclined cutting edge serve as an inclined cutting surface to bore an inside of the pavement cut by the pavement cutting edge, thereby cutting the pavement in a frusto-conical shape.
On an upper portion of the triangle-shaped cutting edge, an additional stepwise-cutting face radially projecting may be provided to further cut the frusto-conical surface of the cut pavement in a step shape. In such a way, the step provided on the peripheral surface of the frusto-conically cut section of the pavement supports the cut section so as to prevent the cut section from falling down.
Furthermore, the present invention provides a method for cutting pavement of an asphalt road or a concrete road in a circle for installation of a manhole, by using a cutting blade which has a pavement cutting edge serves as a tip for cutting the pavement and side edges serve as an inclined cutting surface to bore an inside of the pavement cut by the pavement cutting edge, there by cutting the pavement in a frusto-conical shape. Particularly, said cutting blade connected to an end of a radially-projecting arm attached to a driving shaft arranged vertically with respect to a center of the circle, and moved downwardly and simultaneously rotated along a circumference of the circle of the pavement to be cut,
wherein the cutting blade is inclined to the center of the circle to be cut, and cut the pavement in frusto-conical shape.
That is, the method cutting the pavement in a frusto-conical shape by using the aforementioned cutting blade for cutting the pavement.
In addition, the present invention provides a cutting blade for cutting the pavement in a circle, which comprises an cutting edge attached to the bottom of a body of said cutting blade and a radially-projecting stepwise-cutting edge fixed to an upper portion of said cutting edge, and thereby cutting the cut surface of the pavement in a stepped shape.
Further the cutting blade has a radially-protecting stepped portion above a pavement cutting edge fixed to a cutting blade body at a bottom thereof, and cut the pavement in a stepped shape above the frusto-conical shape.
For a cutting blade preferably used for the present invention, a superhard tip like a diamond one is attached to the bottom edge of the cutting blade because of its superior cutting ability and durability.
In addition, the cutting apparatus is not limited to the aforementioned one that has the cutting blade attached to the end of the arm radially projecting from the lower end of the main driving shaft. The cutting blade may be attached to a cutting apparatus for cutting the pavement, which has an annular cutting blade with a cutting edge attached to the lower end of a body of the annular cutting blade and rotates said annular cutting blade horizontally to cut the pavement, or may be attached to a cutting apparatus for cutting the pavement in a circle by rotation of a disc-shaped cutter, so as to cut the pavement in a frusto-conical shape.
Moreover, the cutting apparatus is preferably fixed to a vehicle for transportation use during operation but it is not necessary to mount the apparatus on the loading deck of the vehicle, instead it may be set up on a different pavement place near to the pavement to be cut in a circle.